We complete the structural closure of the Historical Attractor Theory (HAT) by analyzing the conditions under which quantum descriptions based on amplitudes and interference remain valid. We introduce the notions of historical density, local saturation, and incompatibility between histories, and show that these concepts impose intrinsic limits on the coexistence of alternative histories. Mass is reinterpreted as an extensive historical cost associated with the accumulation of persistent records. We demonstrate that beyond a critical saturation threshold, interference-based descriptions lose operational meaning independently of environmental decoherence. This work establishes the structural domain of validity of quantum descriptions and prepares the ground for the introduction of effective historical amplitudes.
sergio leonardo Pradal (Sun,) studied this question.